1. Field of the Invention
This invention relates to pedal powered boats and particularly pedal powered boats using a flexible drive shaft.
2. Description of Related Art
Pedal powered boats have been used for many years in many different situations. Many lakes or ponds in parks have small catamaran-type boats that users pedal leisurely around the pond. Although these boats are fun, they are not very practical, except as amusement.
Standard rowboats can be provided with a pedal-powered motor. These boats are used in areas where electric or gas engines are prohibited or where these types of propulsion are too noisy. Pedal power is silent. Moreover, it is also highly controllable at low speeds, such as those used during fishing. The operator can stop the boat quickly by not pedaling. Moreover, the operator can move a fair distance by pedaling, while still having full use of his or her hands.
Two designs of such pedal powered boats are found in U.S. Pat. Nos. 4,891,024 and 4,943,251. U.S. Pat. No. 4,891,024 to Benjamin shows a boat with a pedal propulsion system. The boat has a thwart that has a seat attached to it. The seat is positioned between a pedal crank system and the transom of the boat. The pedal crank system is attached to a frame that extends forward of the front of the thwart. The other end of the frame is supported by an adjustable post. The pedal system is connected to solid drive shaft that runs from the pedals to the transom. Universal joints in the shaft allow the shaft angle to be adjusted to accommodate the user. At the transom, it connects to a chain-drive motor. The chain drive extends down a shaft to a transmission and propeller. As the pedals turn the first shaft, it in turns rotates the chain drive, which in turn rotates the propeller. The second U.S. pat. No. 4,943,251 to Lerach et al, is a device uses a pedal and solid drive shaft that extends under a seat to a drive unit mounted on the stern of a canoe. This drive using uses gears to transfer the rotation of the drive shaft to the propeller. As in the case of the Benjamin patent, the solid drive shaft has a universal joint to allow the position of the shaft to be adjusted with respect to the seat. Both of these designs suffer from the same problem. Because they use solid shafts, the seats tend to be set high up near the top of the boat. This allows the shaft to extend from the pedal location to the top of the transom while running under the seat. Unfortunately small watercraft often require a low center of gravity to maintain stability. The high seat positions shown in these patents shift the center of gravity, making the boats unstable.
In addition, the use of a pedal and crank system to operate the propulsion system is inefficient. A straight leg thrust provides more power than the round leg motion used with pedals. The circular motion of the pedals requires a lot of space, both vertically and horizontally. The pedals must be placed high enough in the boat so that they clear the bottom of the boat. At the same time, the rotation forms a circle that extends forward and aft of the crank center. This circle may be obstructed by thwarts or seats, which must be removed to accommodate the range of motion needed for the pedals.